[Intel-gfx] [PATCH] drm/i915: Fix build warning in debugfs

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                 -1              364/364              363/364
ILK                 -2              365/366              363/366
SNB                 -1              450/450              449/450
IVB                                  498/498              498/498
BYT                                  289/289              289/289
HSW                                  564/564              564/564
BDW                                  417/417              417/417
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*PNV  igt_drm_import_export_prime      PASS(2, M25M23)      NO_RESULT(1, M23)
 ILK  igt_kms_flip_bcs-flip-vs-modeset-interruptible      DMESG_WARN(1, M26)PASS(6, M26)      DMESG_WARN(1, M26)
 ILK  igt_kms_flip_plain-flip-ts-check-interruptible      DMESG_WARN(2, M26)PASS(3, M26)      DMESG_WARN(1, M26)
*SNB  igt_kms_pipe_crc_basic_read-crc-pipe-A-frame-sequence      PASS(2, M35M22)      DMESG_WARN(1, M22)
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